Inspection apparatus for high temperature environments

ABSTRACT

A bottle inspection method is provided which is capable of compensating for random variations in the orientation and position of objects being inspected, such as glass bottles on a conveyor. The inspection device creates an image of the object and then analyzes the image to determine the amount of variation in orientation and position. The desired measurements are made from the image and then adjusted relative to the variation previously determined. Also provided is an improved housing for the imaging devices which eliminates the need for clear panels which are prone to dirtying.

BACKGROUND OF THE INVENTION

The present invention relates generally to glass bottle production and,more particularly, to a glass bottle inspection apparatus adapted foruse at the hot end of a glass bottle production line.

The manufacture of glass bottles begins with the preparation of rawmaterials. Sand and soda ash are measured in precise quantities, mixedtogether and conveyed to storage silos located over large meltingfurnaces. The mixed materials are continuously metered into the furnacesto replace molten glass which is dispensed from the furnaces aftermelting.

The furnaces are heated by a combination of natural gas and electricityand are operated at a temperature of over 2500 degrees Fahrenheit. Themelted mixture of raw materials forms molten glass which flows from thefurnaces through refractory channels, also known as forehearths, to aposition over bottle forming machines.

A bottle forming machine known in the industry as an "I.S. machine"draws the glass into individual gobs and drops each gob into a blankmold. The blank mold forms a bottle preform, also referred to as aparison. The preform is transferred to a blow mold where it is blown bycompressed air into a bottle. Each blow mold cavity typically containsindicia provided on a bottom wall thereof which embosses each bottlewith code characters indicating the mold cavity in which it was formed.

The molds are lubricated by oil-borne carbon. The hot mold vaporizes theoil and some of the carbon immediately upon contact, leaving most of thecarbon deposited upon the mold. Thus, the area around the mold is anextremely dirty environment filled with oil and carbon vapors andcondensate.

An I.S. machine typically has between six and sixteen individualsections, with each section having from one to four blow mold cavities.Each section may be capable of manufacturing one to four bottles at atime. A typical eight section, triple gob, I.S. machine used in theproduction of beer bottles may produce 270 beer bottles per minute.

After the bottles have been blown, they are transferred from therespective blow mold cavities onto a moving conveyor belt. The bottlesare positioned on the moving conveyor belt in a single line in asequence corresponding to the sequence of the blow mold cavities inwhich the bottles were formed. The finished bottles transferred onto theconveyor from the blow mold are still red hot (approximately 1,000degrees Fahrenheit). These hot bottles are conveyed by the conveyor beltthrough a hot end coating hood where they are chemically treated with astannous chloride compound for strengthening. Vapors from the hot endcoating hood also contribute significantly to the harsh environmentfound at the "hot end" of the bottle production line.

After passing through the hot end coating hood, the hot bottles areconveyed through an annealing oven or lehr where they are reheated andthen cooled in a controlled manner to eliminate stresses in the glass.This annealing process typically takes from 20 to 30 minutes. Theannealing process is the last process which takes place at the hot endof the production line. The portion of the production line downstreamfrom the annealing oven is referred to as the "cold end" of theproduction line. In contrast to the hot end, the cold end is neither hotnor dirty. At the cold end of the production line, bottles are conveyedthrough a series of inspection devices. Typical prior art inspectiondevices include a squeezer which physically squeezes each bottle tocheck its sidewall strength. Another prior art cold end inspectiondevice is referred to in the industry as a total inspection machine orT.I.M. which is sold by Emhart Glass having a business address of 123Day Hill Road, Windsor, Conn. 06095. The total inspection machinephysically engages each bottle and checks the size of the bottle neckopening and the thickness of the bottle sidewall and reads the code onthe bottle bottom wall to determine the mold of origin. On a statisticalsampling basis, the T.I.M. also sends bottles off line to be tested forburst strength, weighing, and measuring. Reports generated from theT.I.M. correlate bottle defects with the mold of origin. Another typicalprior art inspection device is known as a "super scanner" sold by Inex,13327 U.S. 19 North, Clearwater, Fla. 34624. The super scanner operateson each bottle on line. It initially scans a bottle, then engages androtates the bottle approximately 90 degrees and scans it again. Thesuper scanner uses image analysis to perform certain dimensionalparameter checks of the bottle.

At both the T.I.M. and the super scanner inspection stations, defectivebottles may be rejected by a cold end rejection device. After passingthrough the cold end inspection stations, bottles are transferred to acase packer machine, placed into a cardboard carton and conveyed to apalletizer machine for being placed in pallets. Loaded pallets are thenshipped to a filling facility, such as a brewery.

A problem experienced with traditional glass bottle manufacturingoperations as described above results from the fact that the bottleinspection stations are located at the cold end of the bottle productionline. If a particular blow mold cavity begins producing defectivebottles, e.g. as a result of a foreign object in the mold, the firstdefective bottle produced will not be detected until 30 to 40 minutesafter its formation in the blow mold. As a result of this detectiondelay, the defective mold cavity will have continued to produce hundredsof defective bottles during the period between the first defectiveproduction and discovery of the first defective bottle. Furthermore,unless the defect is a defect of the type discovered by the T.I.M.machine which also identifies each bottle with a blow mold, the moldcausing the problem will not be immediately apparent to the operator. Asa result, the production operation must be shut down and each of themold cavities of the I.S. machine must be inspected to detect the originof the problem. Such shut down and inspection may be very time consumingand results in significant production loss in addition to the scrapproduced by the defective mold cavity.

Locating an inspection machine at the hot end of the bottle productionline is difficult for a number of reasons: (1) as a result of theelevated temperature of the bottles at the hot end of the line, anyengagement of the bottles by an inspection machine as is conventionalwith cold end inspectors would result in deformation of the bottlesurface producing an ascetically unacceptable bottle; (2) the heat ofthe bottles at the hot end causes the bottles to glow and would thusmake reading of mold origin indicating characters on the base of thebottle extremely difficult or impossible; (3) the contaminants in theatmosphere at the hot end of the line tend to coat the surface of anyoptical device used to image the bottles rendering imaging difficult orimpossible; (4) the extreme heat and contamination at the hot end of theline is damaging to any electronics used on inspection devicespositioned at the hot end.

A solution to these problems is addressed in U.S. Pat. No. 5,437,702 ofBurns et al. which is hereby specifically incorporated by reference forall that is disclosed therein. This application discloses anon-contacting optical imaging inspection system that is located at thehot end of a bottle line. The optics and electronics employed areshielded from the harsh environment at the hot end of the productionline by a fluid cooled housing. Clear panels in one of the housing wallsenable the imaging devices within the housing to image passing bottleswithout exposing the optics thereof to the harsh environment of the hotend. Fluid jets are provided adjacent to these clear panels in order toprevent contaminants from building up on the outer surface of thepanels. Monitoring signals from the I.S. machine and the bottle conveyorare processed by data processing apparatus to determine the mold oforigin of each bottle which is being imaged, thus obviating the need toread indicia on the surface of a glowing bottle. The image data fromeach bottle is analyzed to determine whether or not the bottle isdefective.

Although this machine generally works well, difficulties have beenexperienced in determining the orientation of a bottle that is beinginspected. Because the bottles cannot be physically contacted, theirposition relative to the inspection apparatus cannot be precisely set.Variations in the distance between a bottle being imaged and theinspection apparatus result in errors in bottle parameter measurementsbeing taken by the inspection device. Also, because of the relative highspeed of the bottle conveyor, the bottles are often bouncing when theinspection process is being carried out. Due to this bouncing, the exactorientation of a bottle when it is being inspected cannot be accuratelydetermined. This variation in orientation also results in errors whenmeasuring bottle parameters.

It is also been found that, despite the use of the fluid jets describedabove, the clear panels of the housing still occasionally becomedirtied, requiring maintenance and/or resulting in degradation ofperformance.

SUMMARY OF THE INVENTION

The present invention is directed to an inspection device and methodwhich is capable of compensating for random variations in theorientation of objects being inspected. The inspection device acquiresan image of the object and then searches the image for a predeterminedknown characteristic of the object. The orientation of the image of thecharacteristic is then measured and compared to the actual knownorientation of the characteristic to determine the deviationtherebetween. The desired measurements are then made from the image ofthe object. These measurements are then adjusted relative to thedeviation previously determined to arrive at the actual measurements ofthe object being inspected.

The present invention is also directed to an inspection device andapparatus which is capable of compensating for random variations in theposition of objects being inspected. The inspection device adjusts theimage of the object according to its location within the field of viewof the imaging device to compensate for longitudinal variations inposition. The inspection device compares image positioning from twoimaging devices to compensate for transverse variations in position.

The inspection device also includes an improved housing for the imagingdevices and associated electronics. This housing eliminates the clearpanels described previously which are subject to dirtying. Openings areprovided in place of these panels. The housing is maintained at apositive pressure in order to insure that no outside dirt or othercontaminates infiltrate the housing through the openings. The housingmay also be designed so as to minimize the required size of this openingor openings, so as to minimize the amount of pressurized fluid requiredto maintain the housing at a positive pressure.

BRIEF DESCRIPTION OF THE DRAWING

An illustrative and presently preferred embodiment of the invention isshown in the accompanying drawing in which:

FIG. 1 is a schematic diagram of a glass bottle production line;

FIG. 2 is a schematic top plan view of a hot bottle inspection apparatuswith its top member removed for clarity and a portion of an associatedconveyor belt;

FIG. 3 is a schematic top plan view of another embodiment of the hotbottle inspection apparatus shown in FIG. 2;

FIG. 4 is a schematic front elevation view of a defective bottle;

FIG. 5 is a schematic front elevation view of a non-defective bottle;

FIG. 6 is a schematic front elevation view illustrating the process usedto analyze a bottle that is randomly oriented;

FIG. 7 is a flow chart illustrating the steps taken to compensate forrandomly oriented bottles.

FIG. 8 is a plan view of the imaging device of FIG. 2 schematicallyillustrating a bottle that is transversely misaligned.

FIGS. 9A, 9B and 9C schematically illustrate a bottle image from a firstimaging device, a bottle image from a second imaging device and acombined bottle image, respectively, when the bottle being imaged istransversely misaligned closer to the imaging devices.

FIGS. 10A, 10B and 10C schematically illustrate a bottle image from afirst imaging device, a bottle image from a second imaging device and acombined bottle image, respectively, when the bottle being imaged istransversely aligned.

FIGS. 11A, 11B and 11C schematically illustrate a bottle image from afirst imaging device, a bottle image from a second imaging device and acombined bottle image, respectively, when the bottle being imaged istransversely misaligned further from the imaging devices.

FIG. 12 is a schematic top plan view of another embodiment of the hotbottle inspection apparatus shown in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

In general, the invention may pertain to a method for determining atleast one unknown characteristic of an object 52. The method may includethe steps of acquiring a first image of a first feature 140 of theobject, acquiring a second image of a second feature 142, 144 of theobject, analyzing the first image to determine the orientation of thefirst feature 140, analyzing the second image to determine a secondimage measurement and adjusting the second image measurement relative tothe orientation to determine the unknown characteristic.

The invention may also include a method of determining the orientationof an object 52 which includes the steps of creating a first image ofthe object 52 with a first imaging device 102, analyzing the first imageto determine a first orientation of the object 52 in a first plane,creating a second image of the object 52 with a second imaging device104, analyzing the second image to determine a second orientation of theobject 52 in a second plane and calculating the true orientation of theobject 52 based upon the first orientation, the second orientation, andthe angle between the first and second planes.

The invention may also include a method of determining at least oneunknown characteristic of an object 52 which may be randomly positioned.The method may include the steps of acquiring a first image of theobject 52 with a first imaging device 102 acquiring a second image ofthe object 52 with a second imaging device 104, comparing the firstimage with the second image to determine differences therebetween causedby the position of the object 52 relative to the imaging devices 102,104, adjusting the images relative to the differences to provide atleast one corrected image of the object 52 and measuring the correctedimage to determine the unknown characteristic.

The invention may also pertain to an apparatus 64 for measuring at leastone unknown characteristic of objects 52 being conveyed along an objectpathway on a conveyor 12. The apparatus may include an enclosure 100located adjacent the conveyor 12. The enclosure 100 is pressurized to apressure higher than that of the surrounding atmosphere. At least onewindow 110 is provided in the enclosure 100. At least one imagegenerating device 102 is located in the enclosure 100 and aimed throughthe window 110 at a point 50 within the object pathway. The window 110comprises an unobstructed opening.

The invention may also pertain to an apparatus 64 for measuring at leastone unknown characteristic of an object 52 being conveyed along anobject pathway on a conveyor 12. The apparatus may include a firsttarget area 134 located along the object pathway and a second targetarea 132 located along the object pathway. A first imaging device 102and a second imaging device 104 are provided. A first line of sight 103exists between the first imaging device 102 and the first target area134. A second line of sight 105 exists between the second imaging device104 and the second target area 132.

Having thus described the method and apparatus for measuring unknowncharacteristics of an object in general, further features thereof willnow be specifically described.

FIG. 1 is a schematic illustration of a glass bottle production line 10.The production line comprises a conveyor 12 which defines a bottleconveyance path. The conveyor moves bottles downstream in direction 14.A conveyor monitor assembly 16 which may be, for example, a conventionalelectronic encoder mounted on a conveyor motor shaft, monitors theconveying movement of conveyor 12 and produces a conveyor displacementsignal 18 representative thereof. In most bottle production lines theconveyor 12 is mechanically linked to the drive mechanism of the blowmold such that conveyor speed is always directly proportional to thespeed of operation of the blow mold. In such a case any device whichmonitors mold displacement, for example, an incremental encoder mountedon the shaft of the mold drive unit, would also indicate conveyordisplacement and is to be considered a conveyor monitor.

A blow mold assembly 30 comprises a plurality of mold cavity portions32, 34, 36, etc. The blow mold assembly 30 may comprise a portion of aconventional I.S. machine. The blow mold assembly 30 is positioned at anupstream end 38 of conveyor 12. A mold monitor assembly 42 generates amold transfer signal 44 each time the blow mold 30 transfers bottlesonto conveyor 12. Bottles 52, 54, 56, etc. are produced by mold cavityportions 32, 34, 36, etc. and are transferred to conveyor 12 in singlefile in a sequence corresponding to the sequence of their respectiveblow mold cavities of origin. The bottles 52, 54, 56 may be formed withindicia thereon indicative of the blow mold cavity of origin. Thebottles 52, 54, 56, etc. are transferred onto the conveyor 12 at anelevated temperature which may be approximately 1000 degrees Fahrenheitsuch that the bottles are glowing.

A hot coating hood 62 is positioned at a station along the conveyor 12 ashort distance downstream, e.g. 10 feet, from the blow mold 30.

A hot bottle inspection apparatus, also referred to herein as a hotbottle inspector 64, is positioned at a fixed station along the conveyorwhich may be a short distance, e.g. two feet, downstream from the hotcoating hood 62. The hot bottle inspector 64 may thus be located in anextremely hot and dirty environment at the hot end 80 of the productionline. A remote computer 66 removed from the harsh environment at the hotend of the production line is operably connected to the hot bottleinspector 64 and is accessible to a production line operator. Arejection device 68 may be positioned immediately downstream from thehot bottle inspector 64 and is operable to remove bottles from theconveyor in response to commands from the hot bottle inspector 64.

An annealing oven 70 of a conventional type may be positioned downstreamof the rejection device 68 and defines, at its downstream end portion72, the terminal end portion of the "hot end" 80 of the bottleproduction line 10. In a typical production line used for producingglass beer bottles, the period of time elapsing from the transfer of abottle onto the conveyor 12 by the blow mold 30 to the exit of thatbottle from the downstream end 72 of annealing oven 70 may be thirtyminutes.

The portion of the production line 10 located downstream of theannealing oven exit 72 constitutes the "cold end" 82 of the productionline. The cold end of the production line may comprise conventional coldend inspection devices 84, 86, 88 such as a squeezer, a T.I.M. machine,and a super inspector machine such as previously described in the"Background of the Invention" section of this application. The first ofthese cold end inspectors 84 may be positioned, e.g. 100 feet,downstream from the exit 72 of annealing oven 70. A conventional packingassembly 92, such as described above, may be provided downstream fromthe cold end inspection devices 84, 86, 88.

As best illustrated by FIG. 2, the hot bottle inspection apparatus 64comprises a "parallelepiped-shaped" housing 100. This housing contains afirst imaging device 102 and a second imaging device 104.

Housing 100 may comprise front wall 109, first side wall 111, secondside wall 113 and rear wall 115. The housing 100 may also include a topwall member, not shown. Housing 100 may have a length "a" of about 4', awidth "b" of about 2' and a height of about 4'.

A data connection 106 is provided for transmitting the images acquiredby first imaging device 102 and second imaging device 104 to remotecomputer 66. Housing 100 may be insulated in order to withstand theintense heat of the hot end area 80. Pressurized cooling fluid issupplied to the housing 100 via fluid line 108. Fluid line 108 maysupply a flow of pressurized filtered air to the housing for coolingpurposes in a manner as described in the previously referenced U.S.patent application Ser. No. 111,115.

Opening 110 is provided in the front wall 109 of housing 100 to allow aline of sight 103 between the bottle 52 and first imaging device 102.Opening 112 is provided in the front wall 109 of housing 120 to allow aline of sight 105 between bottle 52 and second imaging device 104.Leaving these areas open, rather than covering them with clear panels,obviates the problem previously described regarding the panels becomingdirty. Openings 110 and 112 may each measure about 1 inch by 1 inch.

FIG. 2 shows a series of bottles such as bottles 52, 54 and 56 movingalong conveyor 12 past housing 100 in the direction indicated by thearrow 14. As a bottle, such as bottle 52 in FIG. 2, moves into thetarget site 50, strobe light 94 is energized thus causing the imagingdevices 102 and 104 to produce images of the bottle 52. The computer 66then combines the images to arrive at a composite image as iswell-known.

As previously described, the bottle forming "I.S. machine" generatessignals in a well-known manner. Since the number of bottle molds withinthe I.S. machine is known, computer 66 can use these pulses to determinewhen each bottle is formed and thus when to energize the strobe light94. Since the order of bottles on the conveyor 12 corresponds to themold order in the I.S. machine, the computer 66 is also able tocorrelate acquired image data to the I.S. machine mold which formed thebottle being imaged. In this manner, bottle conditions detected by thehot bottle inspection apparatus can be correlated to a specific mold.

In one example, the I.S. machine may generate one pulse per revolutionand may produce 10 bottles per revolution. In this case, computer 66would know that 10 bottles are produced per I.S. machine pulse. The useof this type of bottle tracking system obviates the need forphotosensors or other physical detectors which would be adverselyaffected by exposure to the harsh environment of the hot end.

In operation, cooling fluid is introduced through fluid line 108 at arate great enough to prevent dirt and outside air from the bottle hotend 80 from entering the housing 64. The fluid entering the housing 100maintains the interior of the housing at a pressure higher than that ofthe outside atmosphere. Although fluid will escape through the openings110 and 112, new cooling fluid is introduced through fluid line 108 at arate great enough to compensate for this escaping fluid. Thisarrangement eliminates the need for a discharge orifice in the housingas disclosed in the previously referenced U.S. Pat. No. 5,437,702. Thisarrangement also eliminates the need for the maintenance previouslyrequired for cleaning the clear panels. The cooling fluid may be in theform of compressed air.

FIG. 3 illustrates an alternative embodiment of the invention in which asingle opening 122 is provided in a housing 120 to accommodate bothlines of sight 103 and 105. Providing only one opening is advantageoussince less cooling air escapes from one opening than escapes from twoopenings. Since less cooling air escapes, less cooling air needs to besupplied to the housing 120.

Housing 120 contains a first imaging device 102 and a second imagingdevice 104. Housing 120 may comprise front wall 121, first side wall123, second side wall 125 and rear wall 127. The housing 120 may alsoinclude a top wall member, not shown. Housing 120 may have a length "c"of about 2', a width "d" of about 2' and a height of about 4'.

A data connection 106 is provided for transmitting the images acquiredby first imaging device 102 and second imaging device 104 to remotecomputer 66. Housing 120 may be insulated in order to withstand theintense heat of the hot end area 80. Pressurized cooling fluid issupplied to the housing 120 via fluid line 108. Fluid line 108 maysupply a flow of pressurized filtered air to the housing for coolingpurposes as described in the previously referenced U.S. patentapplication Ser. No. 111,115.

An opening 122 is provided in the front wall 121 of housing 120 to allowa line of sight 103 between the first imaging device 102 and target site134 located on conveyor 12. Opening 122 also allows a line of sight 105between second imaging device 104 and target site 132 located on theconveyor 12. The imaging devices 102 and 104 are configured withinhousing 120 so that their lines of sight 103 and 105 cross in thevicinity of the opening 122 as shown in FIG. 3. Configuring the imagingdevices in this manner allows the use of one relatively small opening122 in housing 120, thus reducing the loss of cooling air from housing120.

Because of the configuration of imaging devices 102 and 104 describedabove, each imaging device will image a different bottle at any giventime. In order to combine the proper images from imaging devices 102 and104, the remote computer 66 stores image data for a particular bottlefrom imaging device 104 until the same bottle moves into a positionwhere it is imaged by imaging device 102. The computer then assemblesthe image data from the two imaging devices 102 and 104 to obtaincomplete data for each bottle.

FIG. 3 shows a series of bottles such as bottles 124, 126, 128, and 130moving along conveyor 12 past housing 120 in the direction indicated bythe arrow 136. As a bottle, such as bottle 124 in FIG. 3, moves into thetarget site 132, strobe light 138 is energized thus causing imagingdevice 104 to produce an image of the bottle 124. This image is storedby the computer 66 until the bottle 124 moves into the target site 134and strobe light 140 is energized, thus causing imaging device 102 toproduce an image of the bottle 124. The computer then combines thestored image from imaging device 104 with the newly acquired image fromimaging device 102 to arrive at a complete image of bottle 124. Thisprocess is repeated for each bottle conveyed by the conveyor 12. Bottlesare tracked by the computer 66 using I.S. machine pulses in a manner aspreviously described.

Opening 122 may measure about 1" inch by 1 inch. In operation, coolingfluid is introduced through fluid line 108 at a rate great enough toprevent dirt and outside air from the bottle hot end 80 from enteringthe housing 120. The fluid entering the housing 120 maintains theinterior of the housing at a pressure higher than that of the outsideatmosphere. Although fluid will escape through the opening 122, newcooling fluid is introduced through fluid line 108 at a rate greatenough to compensate for this escaping fluid. It has been found thatsupplying cooling fluid in the form of compressed air at a rate of about2 standard cubic feet per minute is sufficient given the size of thehousing 120 and the opening 122 as described above. The compressed airmay be supplied to housing 120 at a temperature of about 30 degreescelsius.

With respect to either housing 100 or housing 120, the imaging devices102 and 104 may be located so that the center of their lenses arevertically aligned with the plane of the top of the conveyor 12. Thisresults in the imaging devices being located substantially below theplane of the conveyor. Since heat rises, this location is cooler andthus less damaging to the imaging devices. This location also allows theplane of the conveyor to be conveniently used as a reference plane whenanalyzing bottle image data.

In another embodiment, as illustrated in FIG. 12, the hot bottleinspection system housing may actually comprise two separate housingunits 100a, 100b, one for each imaging device 102, 104, respectively.This embodiment may be configured as shown in FIG. 2 except that aseparate housing is provided for each imaging device 102, 104. Thesehousings may each be parallelepiped-shaped and have a length of about6", a width of about 6" and a height of about 6" and be otherwiseconstructed in substantially the same manner as the previously describedhousings 100, 120. The use of two separate housings may make personnelaccess to the bottle line easier in some situations.

Correction for Orientation

The general technique of imaging of bottles onto photoelectric devicessuch as CCDs (charge couple devices) and the subsequent analysis of thedata signal to measure various bottle parameters is well known in theart. It has been found, however, that measuring bottles at the hot end80 of a bottle production line 10 presents problems which have notpreviously been solved.

As a result of the elevated temperature of the bottles at the hot end 80of the production line 10, any engagement of the bottles by aninspection machine, as is conventional with cold end inspectors, wouldresult in deformation of the bottle surface producing an asceticallyunacceptable bottle. This, along with the relatively high speed ofbottle production line conveyors means that the bottles are oftenbouncing when a hot end inspection process is being carried out. Due tothis bouncing, the exact orientation of a bottle when it is beinginspected cannot be accurately determined.

The present invention overcomes this difficulty by first analyzing thebottle image to find a known feature of the bottle. The orientation ofthis feature, and thus the entire bottle, is then determined. Thedesired bottle measurements are then made and adjusted relative to theorientation of the known feature. This allows true measurements to beachieved even on randomly oriented bottles, such as bouncing bottles.

One example of a particular physical parameter which may be determinedby the imaging device of the present invention is the degree to whichthe sidewalls of a bottle are perpendicular to its base.

FIG. 4 schematically illustrates a bottle 150, the sidewalls 154, 156 ofwhich are not perpendicular to its base 160. This defective condition iscommonly referred to as "lean" and bottles exhibiting this condition arecommonly referred to as "leaners". It should be noted that the leandepicted in FIG. 4 has been greatly exaggerated for purposes ofillustration. FIG. 5 shows a non-defective bottle 170 exhibiting noperceptible lean.

The lean measured by the hot bottle inspection apparatus 64 may becompared with pre-determined values and any bottle having parametersexceeding a fixed tolerance from this value is determined by the systemto be defective. It is noted, however, that, in the case of leaners,detecting even a slight lean that is within tolerance can be useful tobottle line process control. Leaners generally occur when the bottleformation temperature becomes too high. This high temperature causes theglass to be too soft and, thus, leaners occur. Accordingly, earlydetection of in-tolerance leaners can provide the bottle line operatorswith information indicating that the bottle formation process isbecoming too hot. Adequate corrective action can then be taken toprevent further overheating and the occurrence of reject-level leaners.

Referring again to FIG. 2, it can be seen that first imaging device 102and second imaging device 104 image the bottle 52 from differentdirections. This ensures that a leaner will be detected even if it isleaning directly toward or away from one of the imaging devices. In sucha case, the other imaging device would still detect the lean.

The method employed to compensate for bottle orientation will now bedescribed in detail. FIG. 6 illustrates an image of a bottle 138generated, for example, by first imaging device 102. The bottle 138 wasimaged while it was bouncing and thus is shown in a random orientationin FIG. 6.

Bottle lean may be characterized by the deviation of the center line AAof a bottle from vertical. In other words, deviation may be described asthe difference between the horizontal location of the bottle centerlineAA near the base 140 of the bottle and the horizontal location of thebottle centerline AA near the top of the bottle. If these horizontallocations are identical, then the bottle exhibits no lean. If they aredifferent, however, then the bottle is a leaner and the magnitude ofthis horizontal difference characterizes the amount of lean.

A specific method for measuring lean will now be described in detailwith reference to FIG. 6. FIG. 7 is a block diagram illustrating thismethod.

First, the image is analyzed to determine if there is any light showingbeneath the base 140 of the bottle image 138. If no light is showing,this means that the bottle is setting flat on the conveyor 12 and is notbouncing. If light is showing, as in the case of FIG. 6, this means thatthe bottle is not setting flat on the conveyor and compensation must bemade for the orientation of the bottle due to bouncing.

If the bottle is bouncing, then the "dynamic offset" is calculated. Thedynamic offset is the amount of measured lean caused by the orientationof the bottle. To calculate the dynamic offset, the base 140, left edge142 and right edge 144 of the bottle are first located. Next a point"BL" is located on the base 140 of the bottle. The point BL is definedas a point located along the base 140 of the bottle at a predetermineddistance in from the left edge 142 of the bottle. It is not desirable touse the actual corner of the bottle for the point BL since bottlecorners are often rounded, making a precise location in this areadifficult.

A point "BR" is then located on the base 140 of the bottle. The point BRis defined as a point located along the base 140 of the bottle at apredetermined distance in from the right edge 144 of the bottle. Both ofthe points BL and BR may be located the same distance in from theirrespective edges. This distance may, for example, be about 0.5 inches.

The dynamic offset is then calculated as:

    (BLx-BRx)/(BLy-BRy)×(2y-1y)

where BLx is the location along the x-axis of point BL, BRx is thelocation along the x-axis of point BR, BLy is the location along they-axis of point BL, BRy is the point along the y-axis of point BR and 2yand 1y are predetermined heights above the plane of the conveyor 12 usedto measure bottle lean as further described below.

After the dynamic offset is calculated (or if no dynamic offset iscalculated because the bottle was not bouncing when imaged), points 1Land 1R are located. Point 1L is the point where the left edge 142 of thebottle image is found at a predetermined height 1y above the plane ofthe conveyor 12. Point 1R is the point where the right edge 144 of thebottle image is found at the same height 1y above the plane of theconveyor 12. For purposes of example, the height 1y may be about 1.25inches.

The location of the horizontal center 1C of points 1L and 1R is thencalculated as the point having a y location equal to 1y and an xlocation equal to:

    (1Lx+1Rx)/2

where 1Lx is the location along the x-axis of point 1L and 1Rx is thelocation along the x-axis of point 1R.

Next, points 2L and 2R are located. Point 2L is the point where the leftedge 142 of the bottle image is found at a predetermined height 2y abovethe plane of the conveyor 12. Point 2R is the point where the right edge144 of the bottle image is found at the same height 2y above the planeof the conveyor 12. For purposes of example, the height 2y may be about6 inches.

The location of the horizontal center 2C of points 2L and 2R is thencalculated as the point having a y location equal to 2y and an xlocation equal to:

    (2Lx+2Rx)/2

where 2Lx is the location along the x-axis of point 2L and 2Rx is thelocation along the x-axis of point 2R.

The points 1Cx and 2Cx lie along the centerline AA of the bottle and,thus, together define the centerline AA. The measured lean is thencalculated as the difference in horizontal location of the center points1Cx and 2Cx:

    2Cx-1Cx

Next, the dynamic offset, if any, is subtracted from the measured leanto arrive at the true bottle lean. Since the dynamic offset representsthe lean attributable to the bottle's orientation on the conveyor,subtracting out this lean will result in the lean that is inherent inthe bottle itself.

The above method is carried out for each of the imaging devices 102 and104. The bottle lean calculated for each imaging device is then combinedto arrive at a combined true bottle lean as will now be described.

Imaging devices 102 and 104 are arranged such that their lines of sight103 and 105, respectively cross at right angles to one another, FIGS. 2and 3. Since each imaging device can only measure lean perpendicular toits line of sight, this means that the lean measured by imaging device102 will always be at a right angle to the lean measured by imagingdevice 104. Since two right angle component of the true lean are known,the Pythagorean theorem can be used to calculate the combined true leanas:

    (L1.sup.2 +L2.sup.2).sup.1/2

where L1 is the true lean calculated based on the image from firstimaging device 102 and L2 is the true lean calculated based on the imagefrom second imaging device 104.

The combined true bottle lean is then compared to the allowablespecification. If the combined true lean exceeds the allowable lean,then the bottle is rejected by rejection device 68. If, however, thecombined true lean is within acceptable limits, the bottle is allowed tocontinue on the conveyor 12 toward the cold end 82 of the bottleproduction line.

The combined true lean information may be made available to the bottleproduction line operators even in cases where the lean is found to bewithin allowable limits. This allows the operators to observe and toreact to any trend in the combined true lean measurements. Increasinglean, for example, may indicate that the bottle forming process isbecoming too hot. An operator, observing such an increase, can takeappropriate steps to lower the temperature of the bottle forming processbefore bottles having rejection level defects are formed. Such feedbackof bottle lean information, thus, allows avoidance of potential rejects.Alternatively, a computer may be used to observe and automatically reactto such trend information.

In addition to the dynamic offset described above, a static offset mayalso be subtracted from the measured lean to arrive at the true bottlelean. Static offset is the offset measured when an in-specificationbottle is placed flat on the conveyor 12, while the conveyor is notmoving. Static offset accounts for errors in the hot bottle inspectionsystem itself that do not change from bottle to bottle. For example,static offset may account for any misalignment between the imagingdevices 102, 104 and the bottle conveyor 12.

Static offset may also account for lens aberration. Each imaging device102, 104 contains a lens as is well-known. All lenses display somedegree of aberration, or distortion in some areas of the lens. Staticoffset accounts for such aberration. Subtracting the static offset inthis manner also allows less expensive lenses to be employed. Lessexpensive lenses tend to exhibit more aberration than do more costlylenses. Since this aberration is static and predictable, however, usinga static offset, as described above, allows less expensive lenses to beused while still ensuring that accurate bottle lean information can beobtained.

Although the bottle inspection method has been described with respect toobtaining two center points 1C and 2C, it is noted that a greater numberof points can be evaluated if desired. If a greater number of points areused, the lean can be calculated by taking the average of the individualleans calculated between each of the points.

Using a greater number of points also facilitates the detection of otherbottle abnormalities such as bulges. If a bulge exists in the sidewallof a bottle, this will cause the center point at this location to beoffset from the other center points thus indicating that a problemexists in this area.

In addition to bottle lean information, the procedure described abovemay also be used to measure actual bottle dimensions at variouslocations. Once the bottle lean is known, the true bottle width, e.g.,may be calculated using trigonometry. An example of such a calculationis described below with respect to FIG. 6.

For purposes of this example, the "lean angle" is the angle formedbetween the base 140 of the bottle and the conveyor 12. The lean anglemay be calculated using any number of trigonometric functions and thebottle measurement data which has been collected as previouslydescribed. The lean angle may, for example, be calculated as follows:

    lean angle=tan.sup.-1 ((BLy-BRy)/(BLx-BRx))

Once calculated, the lean angle may then be used to derive the truebottle dimensions from the measured image data. For example, the truebottle width at the point 1L may be calculated as follows:

    true width=cos(lean angle)×(1Lx-1Rx)

Other true bottle dimensions may be calculated in a similar manner oncethe lean angle is known.

Correction for Longitudinal Misalignment

It has been found that the position of a bottle such as bottle 52 onconveyor 12 can vary from bottle to bottle. This is because, as bottlesare placed onto the conveyor by the blow mold 30, they are not alwaysplaced in exactly the same position on the conveyor. Accordingly, theposition of a particular bottle can vary both in a transverse direction114 (in a direction perpendicular to the direction of conveyor movement)and also in a longitudinal direction 116, perpendicular to thetransverse direction as shown in FIG. 2.

Referring to FIG. 2, when a bottle 52 is perfectly alignedlongitudinally, it will be located at the target site 52 when the strobe94 is energized. In this case, the bottle 52 will be longitudinallyequidistant from the imaging devices 102, 104. When a bottle 52 variesin longitudinal direction 116, however, it will either be downstream (inthe direction of the arrow 14) or upstream (in the direction oppositethe arrow 14) of the target site 50 when the strobe 94 is energized. Ifthe bottle 52 is downstream, it will be closer to imaging device 104 andfurther from imaging device 102. Conversely, if the bottle 52 isupstream, it will be closer to imaging device 102 and further fromimaging device 104.

When the bottle 52 is closer to one imaging device than the other, theimage of the bottle acquired by the closer imaging device will be largerthan the image of the bottle acquired by the further imaging device.When this condition is detected by the computer 66, the bottle beingimaged is longitudinally misaligned. By measuring the amount ofdifference in bottle image size, the computer 66 can determine theamount of longitudinal misalignment and correct the image sizeaccordingly.

Correction for Transverse Misalignment

Referring to FIGS. 2 and 8, when a bottle 52 is perfectly aligned in atransverse direction 114, it will be located at the target site 50 whenthe strobe 94 is energized. When a bottle 52 varies in transversedirection 114, however, it will either be closer to, e.g., position 202,or further from, e.g., position 200, the imaging devices 102, 104, FIG.8.

FIGS. 9A-11A schematically illustrate the image 194 acquired by theimaging device 104 which includes the bottle image 204. FIGS. 9B-11Billustrate the image 192 acquired by the imaging device 102 whichincludes the bottle image 202. To determine transverse location, thecomputer 66 combines the image 192 and the image 194 from the imagingdevices 102, 104 into one image 206, FIGS. 9C-11C. If the bottle 52 isperfectly aligned transversely, as shown in FIGS. 2 and 10, the image ofthe bottle acquired from each imaging device 102, 104 will overlap. Thecombined image will, thus result in only one bottle image as seen inFIG. 10C.

If, however, the bottle 52 is transversely misaligned closer to theimaging devices 102, 104, e.g. at the position 202, FIG. 8, the bottleimage 202 acquired by imaging device 102 will be shifted to the left(since the bottle has shifted to the left in the field of view ofimaging device 102). This is best illustrated in FIG. 9B.

In a similar manner, the bottle image 204 acquired by imaging device 104will be shifted to the right (since the bottle has shifted to the rightin the field of view of imaging device 104). This is best illustrated inFIG. 9A.

In such a misaligned configuration, the combined image 206, FIG. 9C willresult in the individual bottle images 202, 204 not overlapping. Inother words, the edges of the bottle images 202, 204 acquired fromimaging devices 102, 104 will not overlap. Specifically, the bottleimage 202 acquired by the imaging device 102 will be shifted to the leftrelative to the bottle image 204 acquired by the imaging device 104 asshown in FIG. 9C.

If the bottle 52 is transversely misaligned further from the imagingdevices 102, 104, e.g., at the position 200, FIG. 8, the bottle image202 acquired by imaging device 102 will be shifted to the right (sincethe bottle has shifted to the right in the field of view of imagingdevice 102). This is best illustrated in FIG. 11B.

In a similar manner, the bottle image 204 acquired by imaging device 104will be shifted to the left (since the bottle has shifted to the left inthe field of view of imaging device 104). This is best illustrated inFIG. 11A.

In such a misaligned configuration, the combined image 206, FIG. 11Cwill result in the individual bottle images 202, 204 not overlapping. Inother words, the edges of the bottle images 202, 204 acquired fromimaging devices 102, 104 will not overlap. Specifically, the bottleimage 202 acquired by the imaging device 102 will be shifted to theright relative to the bottle image 204 acquired by the imaging device104 as shown in FIG. 11C.

Accordingly, the computer 66 can detect that a transverse misalignmentcondition exists and can determine in which direction the misalignmentoccurs. By measuring the distance between the bottle images 202, 204,the computer 66 can also measure the amount of misalignment. Once theamount of misalignment is known, the computer 66 may align the images202, 204 and adjust the size of the image to compensate for thetransverse misalignment. In other words, if the computer 66 detects thatthe bottle 52 is transversely misaligned further from the imagingdevices 102, 104, e.g. at the position 200, the combined bottle imagemay be enlarged in accordance with the amount of transversemisalignment. In a similar manner, if the computer 66 detects that thebottle 52 is transversely misaligned closer to the imaging devices 102,104, e.g. at the position 201, the combined bottle image may be reducedin accordance with the amount of transverse misalignment.

Upon initial start-up of the inspection apparatus 64, it may becalibrated by running bottles of known dimensions and characteristicsthrough the inspection apparatus. The computer 64 can then correlate theactual size of these bottles to the size of their images generated bythe inspection apparatus 64. The computer 66 may then use thisrelationship to measure characteristics of unknown bottles as describedabove.

Although the above methods for correction of orientation and positionhave been described with respect to bottle inspection, these methodscould be used for any inspection task in which the objects beinginspected are not uniformly oriented and/or positioned.

While an illustrative and presently preferred embodiment of theinvention has been described in detail herein, it is to be understoodthat the inventive concepts may be otherwise variously embodied andemployed and that the appended claims are intended to be construed toinclude such variations except insofar as limited by the prior art.

What is claimed is:
 1. Apparatus for measuring at least one unknowncharacteristic of objects being conveyed along an object pathway on aconveyor comprising:(a) an enclosure located adjacent said conveyor; (b)said enclosure pressurized to a pressure higher than that of thesurrounding atmosphere; (c) at least one window in said enclosure; (d)at least one image generating device located in said enclosure and aimedthrough said window at a point within said object pathway; (e) whereinsaid window comprises an unobstructed opening.
 2. The apparatus of claim1 wherein a cooling fluid supply line is connected to said enclosure. 3.The apparatus of claim 1 wherein there are two windows in said enclosureand two image generating devices located in said enclosure and aimedthrough said windows at a point within said object pathway.
 4. Theapparatus of claim 3 wherein said enclosure is a parallelepiped-shapedhousing having a length substantially equal to 4 feet, a widthapproximately equal to 2 feet, and a height approximately equal to 4feet.
 5. The apparatus of claim 3 wherein said windows each measureapproximately 1 inch by 1 inch.
 6. The apparatus of claim 1 furthercomprising:a. a remote computer; and b. a data connection connected tosaid at least one image generating device and to said remote computer.7. The apparatus of claim 6 wherein said enclosure comprises aparallelepiped-shaped housing having a length substantially equal to 4feet, a width approximately equal to 2 feet, and a height approximatelyequal to 4 feet.
 8. Apparatus for measuring at least one unknowncharacteristic of objects being conveyed along an object pathway on aconveyor comprising:(a) a first enclosure located adjacent saidconveyor; (b) a second enclosure located adjacent said conveyor; (c)each of said first and second enclosures pressurized to a pressurehigher than that of the surrounding atmosphere; (d) a first window insaid first enclosure; (e) a second window in said second enclosure (f)at least a first image generating device located in said first enclosureand aimed through said first window at a point within said objectpathway; (g) at least a second image generating device located in saidsecond enclosure and aimed through said second window at said pointwithin said object pathway; (h) wherein said first and second windowscomprise unobstructed openings.
 9. The apparatus of claim 8 wherein acooling fluid supply line is connected to each of said first and secondenclosures.
 10. The apparatus of claim 8 wherein each of said enclosurescomprises a parallelepiped-shaped housing having a length substantiallyequal to 6 inches, a width approximately equal to 6 inches, and a heightapproximately equal to 6 inches.
 11. The apparatus of claim 8 furthercomprising:a. a remote computer; and b. a data connection connected toeach of said first and second image generating devices and to saidremote computer.